Changes to the scheme came into force in November 2016, introducing cuts to all three forms of civil service exit payout — for voluntary exits, voluntary redundancies and compulsory redundancies — as well as shorter redundancy notice periods for new starters and changes to early access to pension provision.

The proposals were originally put out for consultation in February 2016, and initial rounds of talks were held with all unions to discuss the changes.

A senior Cabinet Office official then wrote to civil service unions in June, proposing a further round of talks and stating that attendance at these discussions would be “taken as a clear commitment” that government’s proposals would form the basis of new arrangements that unions would then recommend to their members.

In a bid to avoid more stringent terms being imposed, unions Prospect and the FDA took part in negotiations, but the PCS, Unite and the Prison Officers’ Association refused to join the talks.

In today’s judgement, Lord Justice Sales and Lady Justice Whipple said: “It was not surprising that [these unions], all of whom were in general opposed to the proposals, were unable to give such a commitment.”

They concluded that the minister had acted unlawfully, and “there was no basis on which the minister was entitled to exclude the PCSU from the consultation.”

The judges also rejected the Cabinet Office’s claim that including these unions would have made no difference to the final agreement.

The judgment states: “It cannot be said that it is highly likely that the outcome would not have been affected if the PCSU had been allowed to participate in the second round of discussions, as it should have been.”

“The safeguard for workers is that they will not have their rights to compensation benefits diminished or removed without a genuine attempt first having been made to secure agreement on that specific issue with their union representatives. These provisions are not concerned only with vague agreements in principle.”

However, judges dismissed a PCS claim that the government did not comply with the Public Sector Equality Duty when introducing the changes. They also disagreed with a further PCS claim that changing civil servants’ compensation entitlements was a violation of the Human Rights Act. Although the judges found that entitlements to benefits under the pre-2016 scheme were "possessions" under that law, they also found that government had an objective reason to change these entitlements because the previous scheme – set up in 2010 – had not delivered the hoped for savings across government.

A Cabinet Office spokesperson said: “The government is carefully considering the judgment and intends to appeal.”

PCS general secretary Mark Serwotka said the ruling was “a major victory for us and all civil servants and shows the value of belonging to a trade union that is prepared to fight back.”

He added: “This is yet another example of how Tory governments treat their own workforce and other public servants with utter contempt. Ministers must have known they were breaking the law by excluding us, yet they went ahead anyway.

“There is no way we would ever allow ourselves be chained in negotiations where the terms are rigged and the outcome fixed in advance, and no right thinking person could expect us to.”

A PCS source told CSW: “We’re looking forward to discussing this judgement with our colleagues in the other civil service unions, they’ll no doubt want to thank us for fighting the case.”

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